Yarn delivery or yarn supply apparatus having a storage drum which is rotatable and carries one or usually a plurality of storage windings have been previously proposed. It is customary to pull off the yarn over the end, or head or the storage drum. This is obtained by locating the yarn guiding eye roughly coaxially to the axis of rotation of the storage drum, and axially spaced from the lower edge thereof. An additional thread guide element is provided which defines the pull-off position at the lower edge of the storage drum when positive yarn guiding is to be achieved. One such system is described in the referenced published German patent application DT-AS No. 2 341 498. When using yarn, or threads or other filamentary material which has S or Z twists, or in general when using yarn which is highly twisted or spiraled, the situation may arise that when the tension decreases below a certain minimum value, the yarn tends to form loops or kinks. Formation of loops or kinks results in irregularities in yarn supply and may lead to immediate, or subsequent stopping of the machine since the run out sensors are operated. It is also possible that the kinks or loops will hook into machine elements causing tearing of the yarn or other filamentary material. The utilization characteristics of highly twisted yarns and yarns of the typed described also depend on the direction of rotation of the storage drum. This causes difficulty since the yarn supply arrangement usually are provided to operate only in one direction of rotation of the storage drum.
It has previously been proposed--see the referenced German disclosure document DT-OS No. 26 08 590--to permit selective utilization of yarn having S or Z twists by locating a pull-off or take-up eye laterally adjacent a storage drum and a predetermined distance below the lower edge thereof so that the yarn or thread being pulled off is guided downwardly with an inclination over the edge of the storage drum. The pull-off guide element need not be an eye; other guide elements can be used. In operation, any loops or kinks in the thread which might arise upon decrease of yarn tension will not result in wrapping or formation of the loops on the storage drum, which might block yarn pull-off; additionally, the arrangement prevents pulling off more than one winding from the storage windings wound on the storage drum.
Some yarns require operation with extremely low thread tension in the region between the storage drum and the utilization position, for example a knitting feed of a circular knitting machine. Particularly, if the yarn is twisted, it has been found that difficulties in pull-off of the yarn may still arise, particularly if the direction of rotation of the storage drum and the direction of twist of the yarn are relatively so arranged that during pull-off at low tension, the yarn tends to form kinks or loops or portions twisted upon itself.